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Research Article
Species diversity and taxonomy of Scytinostroma sensu stricto (Russulales, Basidiomycota) with descriptions of four new species from China
expand article infoYue Li‡, Wei-Qi Xu‡, Shi-Liang Liu§, Ning Yang|, Shuang-Hui He‡
‡ Beijing Forestry University, Beijing, China
§ State Key Laboratory of Mycology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
| Beijing Municipal Research Institute of Eco-Environmental Protection, Beijing, China

Corresponding author: Shuang-Hui He ( heshuanghui@bjfu.edu.cn )

Academic editor: María P. Martín
© 2023 Yue Li, Wei-Qi Xu, Shi-Liang Liu, Ning Yang, Shuang-Hui He.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation: Li Y, Xu W-Q, Liu S-L, Yang N, He S-H (2023) Species diversity and taxonomy of Scytinostroma sensu stricto (Russulales, Basidiomycota) with descriptions of four new species from China. MycoKeys 98: 133-152. https://doi.org/10.3897/mycokeys.98.105632
Open Access

Abstract

Scytinostroma is species-rich genus in Peniophoraceae, Russulales and has been shown to be polyphyletic. In this study, we performed phylogenetic analyses on the core clade of Scytinostroma based on concatenated ITS1-5.8S-ITS2-nrLSU sequence data. Fifteen lineages including four new species from China, Scytinostroma beijingensis, S. boidinii, S. subduriusculum, and S. subrenisporum, were recognized. The genus Michenera was nested within the Scytinostroma s.s. clade in the phylogenetic tree of Peniophoraceae. Sequences of S. portentosum (type species) and S. hemidichophyticum from Europe formed a strongly supported lineage sister to the S. portentosum sample from Canada. It is supposed that the European “S. portentosum” is S. hemidichophyticum, and the former species is restricted in distribution to North America. Scytinostroma duriusculum is supposed to be a species complex. Samples from Sri Lanka (the type locality) formed a lineage sister to those from China, Thailand and Vietnam (described herein as S. subduriusculum) and two samples from France that might represent an undescribed species. The four new species are described and illustrated, and an identification key to all the 14 Scytinostroma s.s. species worldwide is provided. Until now, seven species of Scytinostroma s.s. have been found in China. Our results increased the knowledge of species diversity and taxonomy of corticioid fungi in China.

Key words

corticioid fungi, Peniophoraceae, phylogeny, white rot, wood-decaying fungi

Introduction

The genus Scytinostroma Donk sensu lato (Peniophoraceae, Russulales), typified by S. portentosum (Berk. & M.A. Curtis) Donk, is characterized by resupinate, effused basidiomes with a smooth to tuberculate hymenophore, a dimitic hyphal system with dextrinoid and cyanophilous skeletal hyphae, presence of gloeocystidia in most species, and subglobose to ellipsoid, variably amyloid or inamyloid, smooth basidiospores (Bernicchia and Gorjón 2010; Liu et al. 2018; Stalpers et al. 2021). It is a widely distributed genus with 42 species level names in Index Fungorum (http://www.indexfungorum.org, accessed on 1 January 2023). Morphologically, Scytinostroma can be easily distinguished from other genera of Peniophoraceae by having a dimitic hyphal system and smooth basidiospores. It is similar to Vararia P. Karst., which usually differs in having typical dichohyphae (Bernicchia and Gorjón 2010). Liu et al. (2018) demonstrated that Michenera Berk. & M.A. Curtis belonged to Peniophoraceae and was closely related to Scytinostroma. The two genera are similar in some aspects, such as the texture of basidiome, a dimitic hyphal system, presence of gloeocystidia, but species of Michenera have larger basidia and larger, inamyloid, thick-walled basidiospores. Based on morphology, Stalpers et al. (2021) transferred the two species of Michenera to Scytinostroma and treated the former genus as a synonym of the latter.

Larsson and Larsson (2003) and Miller et al. (2006) showed that five species of Scytinostroma, S. galactinum (Fr.) Donk, S. jacksonii Boidin, S. ochroleucum Donk, S. odoratum (Fr.) Donk and S. portentosum (type species), occurred on five distinct branches that are distantly separated in Peniophoraceae. Leal-Dutra et al. (2018) built the genus Baltazaria Leal-Dutra, Dentinger & G.W. Griff. for S. galactinum and other three species, S. neogalactinum Boidin & Lanq., S. eurasiaticogalactinum Boidin & Lanq. and Parapterulicium octopodites Corner. Our preliminary phylogenetic analyses showed that some specimens recently collected from China clustered with S. portentosum (type species) and several other species, which represented the core clade of Scytinostroma. In order to understand the species diversity within this clade, we carried out phylogenetic analyses of Peniophoraceae based on concatenated ITS1-5.8S-ITS2-nrLSU sequence data, focusing on samples of Scytinostroma s.s. worldwide. Fifteen species-level lineages were recognized in the phylogenetic tree. Among them, four lineages are new and here described and illustrated as S. beijingensis, S. boidinii, S. subduriusculum, and S. subrenisporum spp. nov.

Materials and methods

Specimen collection

In situ photos of specimens were taken with a Canon camera EOS 70D (Canon Corporation, Japan). Specimens were dried with a portable dryer, labelled, and then stored in a freezer at minus 40 °C for two weeks to kill the insects and their eggs before proceeding with morphological and molecular studies. Voucher specimens are deposited at the herbarium of Beijing Forestry University, Beijing, China (BJFC).

Morphological studies

Thin, freehand sections were made from dried basidiomes and mounted in 2% (weight/volume) aqueous potassium hydroxide (KOH) and 1% (w/v) aqueous phloxine. Amyloidity and dextrinoidity of hyphae and basidiospores were checked in Melzer’s reagent (IKI). Cyanophily of hyphal and basidiospore walls were observed in 1% (w/v) cotton blue in 60% (w/v) lactic acid (CB). Microscopic examinations were carried out with a Nikon Eclipse 80i microscope (Nikon Corporation, Japan) at magnifications up to 1000×. Drawings were made with the aid of a drawing tube. The following abbreviations are used: IKI– = neither amyloid nor dextrinoid, CB+ = cyanophilous, CB– = acyanophilous, SA+ = positive reaction in Sulphobenzaldehyde, SA– = negative reaction in Sulphobenzaldehyde, L = mean spore length, W = mean spore width, Q = L/W ratio, n (a/b) = number of spores (a) measured from the number of specimens (b). Color codes and names follow Kornerup and Wanscher (1978).

DNA extraction and sequencing

A CTAB plant genomic DNA extraction kit, DN14 (Aidlab Biotechnologies Co., Ltd., Beijing, China) was used to extract total genomic DNA from dried specimens, then amplified by the polymerase chain reaction (PCR), according to the manufacturer’s instructions. The ITS1-5.8S-ITS2 region was amplified with the primer pair ITS5/ITS4 (White et al. 1990) using the following protocol: initial denaturation at 95 °C for 4 min, followed by 34 cycles at 94 °C for 40 s, 58 °C for 45 s and 72 °C for 1 min, and final extension at 72 °C for 10 min. The D1-D2 region of the nucleic ribosomal LSU was amplified with the primer pair LR0R/LR7 (https://sites.duke.edu/vilgalyslab/rdna_primers_for_fungi/) employing the following procedure: initial denaturation at 94 °C for 1 min, followed by 34 cycles at 94 °C for 30 s, 50 °C for 1 min and 72 °C for 1.5 min, and final extension at 72 °C for 10 min. DNA sequencing was performed at Beijing Genomics Institute, and newly generated sequences were deposited in GenBank (https://www.ncbi.nlm.nih.gov/). BioEdit v.7.0.5.3 (Hall 1999) and Geneious Basic v.11.1.15 (Kearse et al. 2012) were used to review the chromatograms and for contig assembly.

Phylogenetic analyses

The dataset of concatenated ITS1-5.8S-ITS2-nrLSU sequences of the Peniophoraceae was analyzed. Amylostereum chailletii (Pers.) Boidin and A. laevigatum (Fr.) Boidin were selected as the outgroup (Larsson and Larsson 2003; Xu et al. 2023). Sequences including those from Larsson and Larsson (2003) were partitioned to ITS1, 5.8S, ITS2 and nrLSU, and then aligned separately using MAFFT v.74 (http://mafft.cbrc.jp/alignment/server/, Katoh et al. 2017) with the G-INS-I iterative refinement algorithm and optimized manually in BioEdit v.7.0.5.3. The separate alignments were then concatenated using Mesquite v.3.5.1 (Maddison and Maddison 2018). The dataset was deposited in TreeBase (http://treebase.org/treebase-web/home.html, submission ID: 30453).

Maximum likelihood (ML) analyses, and Bayesian inference (BI) were carried out by using RAxML v.8.2.10 (Stamatakis 2014) and MrBayes 3.2.6 (Ronquist et al. 2012), respectively. In ML analysis, statistical support values were obtained using rapid bootstrapping with 1000 replicates, with default settings for other parameters. For BI, the best-fit substitution model was estimated with jModeltest v.2.17 (Darriba et al. 2012). Four Markov chains were run for 2,000,000 generations for the dataset; until the split deviation frequency value was lower than 0.01. Trees were sampled every 100th generation. The first quarter of the trees, which represented the burn-in phase of the analyses, were discarded, and the remaining trees were used to calculate posterior probabilities (BPP) in the majority rule consensus tree.

Results

Phylogenetic analyses

The concatenated ITS1-5.8S-ITS2-nrLSU dataset contained 58 ITS and 52 nrLSU sequences from 61 samples, representing 33 ingroup taxa and the outgroup (Table 1), and had an aligned length of 2628 characters. jModelTest suggested GTR+I+G, K80+I, HKY+I+G, GTR+I+G to be the best-fit models of nucleotide evolution for ITS1, 5.8S, ITS2, and nrLSU markers, respectively, for the Bayesian analysis. The average standard deviation of split frequencies of BI was 0.005711 at the end of the run. BI analyses resulted in almost identical tree topologies with the ML analysis. Only the ML tree is provided in Fig. 1 with the likelihood bootstrap values (≥ 50%, first) and Bayesian posterior probabilities (≥ 0.95, second) labelled along the branches.

Table 1.
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Species and sequences used in the phylogenetic analyses. New species are set in bold with type specimens indicated with an asterisk (*).

Species Specimen No. Locality GenBank Accession No. Reference
ITS nrLSU
Asterostroma laxum EL33-99 Estonia AF506410 AF506410 Larsson and Larsson 2003
Asterostroma muscicola KHL9537 Puerto Rico AF506409 AF506409 Larsson and Larsson 2003
Baltazaria galactina CBS 752.86 France MH862034 MH873721 Vu et al. 2019
Baltazaria neogalactina CBS 755.86 French Guiana MH862037 MH873724 Vu et al. 2019
Confertobasidium olivaceoalbum FP 90196 USA AF511648 AF511648 Larsson and Larsson 2003
Dichostereum durum CBS 707.81 France MH861450 MH873192 Vu et al. 2019
Dichostereum effuscatum GG930915 France AF506390 AF506390 Larsson and Larsson 2003
Gloiothele lactescens EL8-98 Sweden AF506453 AF506453 Larsson and Larsson 2003
Gloiothele lamellosa KHL11031 Venezuela AF506454 AF506454 Larsson and Larsson 2003
Lachnocladium schweinfurthianum KM49740 Cameroon MH260033 MH260051 Leal-Dutra et al. 2018
Lachnocladium sp. KHL10556 Jamaica AF506461 AF506461 Larsson and Larsson 2003
Metulodontia nivea NH 13108 Russia AF506423 AF506423 Larsson and Larsson 2003
Peniophora quercina CBS 407.50 France MH856687 MH868204 Vu et al. 2019
Peniophora tristicula He 4775 China MH669235 MH669239 Liu and He 2018
Peniophora versiformis He 3029 China MK588756 MK588796 Xu et al. 2023
Scytinostroma acystidiatum He 5646 China MK625568 MK625494 Present study
Scytinostroma acystidiatum He 5668 China MK625569 MK625496 Present study
Scytinostroma alutum CBS 762.81 France MH861482 MH873221 Vu et al. 2019
Scytinostroma alutum CBS 763.81 France MH861483 MH873222 Vu et al. 2019
Scytinostroma artocreas GHL-2016-Oct USA MH142900 MH204691 Liu et al. 2018
Scytinostroma beijingensis He 7203 China – OQ729729 Present study
Scytinostroma beijingensis He 7668 China – OQ729730 Present study
Scytinostroma beijingensis He 7768* China OQ731943 OQ729731 Present study
Scytinostroma boidinii He 2499 China MK625573 – Present study
Scytinostroma boidinii He 5138 China MK625572 MK625497 Present study
Scytinostroma boidinii He 6911* China OQ731934 OQ729724 Present study
Scytinostroma boidinii He 7465a China OQ731935 – Present study
Scytinostroma boidinii He 7465b China OQ731936 – Present study
Scytinostroma caudisporum CBS 746.86 Gabon MH862030 AY293210 Vu et al. 2019; Binder et al. 2005
Scytinostroma duriusculum He 5748 Sri Lanka OQ865248 – Present study
Scytinostroma duriusculum He 5756 Sri Lanka OQ865249 – Present study
‘Scytinostroma duriusculum’ CBS 757.81 France MH861477 MH873216 Vu et al. 2019
‘Scytinostroma duriusculum’ CBS 758.81 France MH861478 MH873217 Vu et al. 2019
Scytinostroma hemidichophyticum CBS 702.84 Belgium MH861818 MH873509 Vu et al. 2019
Scytinostroma hemidichophyticum CBS 759.81 France MH861479 MH873218 Vu et al. 2019
Scytinostroma hemidichophyticum CBS 760.81 France MH861480 MH873219 Vu et al. 2019
Scytinostroma incrustatum He 2841 China MH142906 MH142910 Liu et al. 2018
Scytinostroma incrustatum He 5368 China MH204689 MH204690 Liu et al. 2018
Scytinostroma portentosum CBS 503.48 Canada MH856447 AF518723 Vu et al. 2019
Scytinostroma portentosum EL11-99 Sweden AF506470 AF506470 Larsson and Larsson 2003
Scytinostroma portentosum GEL3225 – – AJ406488 Langer 2002
Scytinostroma renisporum CBS 771.86 Indonesia MH862051 MH873738 Vu et al. 2019
Scytinostroma renisporum CBS 772.86 Indonesia MH862052 MH873739 Vu et al. 2019
Scytinostroma subduriusculum He 3590 China MK625571 MK625499 Present study
Scytinostroma subduriusculum He 4146 Thailand MK625570 MK625498 Present study
Scytinostroma subduriusculum He 7134 China OQ731937 – Present study
Scytinostroma subduriusculum He 7141 China OQ731938 OQ729725 Present study
Scytinostroma subduriusculum He 7148 China OQ731939 – Present study
Scytinostroma subduriusculum He 7150 China OQ731940 OQ729726 Present study
Scytinostroma subduriusculum He 7657* China OQ731941 OQ729727 Present study
Scytinostroma subduriusculum He 7717 China OQ731942 OQ729728 Present study
Scytinostroma subrenisporum He 4384 China MK625567 MK625495 Present study
Scytinostroma subrenisporum He 4792* China MK625566 MK625493 Present study
Scytinostroma yunnanense CLZhao 10802 China MT611446 – Wang et al. 2020
Scytinostroma yunnanense CLZhao 11010 China MT611447 – Wang et al. 2020
Vararia amphithallica He 4330 China MK674474 MK625542 Present study
Vararia investiens TAA164122 Norway AF506484 AF506484 Larsson and Larsson 2003
Vesiculomyces citrinus He 3716 China KY860369 KY860429 Present study
Vesiculomyces citrinus EL53-97 Sweden AF506486 AF506486 Larsson and Larsson 2003
OUTGROUP
Amylostereum chailletii NH 8031 Sweden AF506406 AF506406 Larsson and Larsson 2003
Amylostereum laevigatum NH 12863 Sweden AF506407 AF506407 Larsson and Larsson 2003
Figure 1. 

Phylogenetic tree of ML analysis from the ITS1-5.8S-ITS2-nrLSU sequences of Peniophoraceae taxa. Branches are labelled with likelihood bootstrap values (≥ 50%, first) and Bayesian posterior probabilities (≥ 0.95, second). New species are set in bold and highlighted.

In the tree, Scytinostroma s.s. clade received a moderately strong support value in ML analysis (bootstrap value = 56) but a strong value in BI (Bayesian posterior probabilities = 1). Four new distinct lineages corresponding to Scytinostroma beijingensis, S. boidinii, S. subduriusculum and S. subrenisporum spp. nov. were recognized. Sequences of S. portentosum and S. hemidichophyticum from Europe formed a strongly supported lineage sister to the S. portentosum sample from Canada. Samples of S. duriusculum from France and those from Sri Lanka (the type locality) formed a lineage sister to S. subduriusculum. Scytinostroma incrustatum (S.H. He, S.L. Liu & Nakasone) K.H. Larss. and S. artocreas (Berk. & M.A. Curtis) K.H. Larss.,which were formerly placed in Michenera, were nested within Scytinostroma s.s. clade.

Taxonomy

Scytinostroma beijingensis Yue Li, S.L. Liu & S.H. He, sp. nov.

MycoBank No: 848268
Figs 2, 3

Type

China, Beijing, Haidian District, Yangtaishan Forest Park, on dead Pyrus tree, 4 September 2022, He 7768 (BJFC 038905, holotype).

Figure 2. 

Basidiomes of Scytinostroma beijingensis a He 7768 (BJFC 038905, holotype) b He 7201 (BJFC 036518) c He 7203 (BJFC 036520) d He 7220 (BJFC 036537) e He 7668 (BJFC 038804) f He 7759 (BJFC 038896). Scale bars: 1 cm (a–f).

Figure 3. 

Microscopic structures of Scytinostroma beijingensis (from the holotype He 7768) a basidiospores b basidia c basidioles d, e gloeocystidia f skeletal hyphae from hymenium g skeletal hyphae from subiculum. Scale bars: 10 µm (a–g).

Etymology

Refers to the type locality in Beijing, China.

Fruiting body

Basidiomes annual, resupinate, widely effused, closely adnate, inseparable from substrate, coriaceous, first as small patches, later confluent up to 12 cm long, 4.5 cm wide, up to 200 µm thick in section. Hymenophore smooth, greyish yellow (4B5) to greyish orange (5B5), unchanged in KOH, not cracked or deeply cracked with age; margin thinning out, adnate, fimbriate, white or concolorous with hymenophore surface. Context yellow.

Microscopic structures

Hyphal system dimitic. Context thickening, compact. Generative hyphae rare, scattered, simple-septate, colorless, thin-walled, 2–3 µm in diam., IKI–, CB–. Skeletal hyphae dominant, colorless to yellow, distinctly thick-walled, moderately branched, 2.5–4 µm in diam., weakly dextriniod, CB+. Catahymenium composed of skeletal hyphae, gloeocystidia, basidia and basidioles. Skeletal hyphae abundant, similar to those in the context, but strongly dextrinoid, frequently dichotomous-branched with acute tips, 1–2 µm wide at lowest part. Gloeocystidia abundant, SA+, with two shapes (1) ventricose, colorless, thin- to slightly thick-walled, mostly embedded, usually with contents, 28–40 × 8–15 µm; (2) subcylindrical, colorless, thin- to slightly thick-walled, mostly projecting beyond the hymenium, usually with contents, 45–65 × 5–7 µm. Basidia subcylindrical, slightly curved, thin-walled, colorless, smooth, with four sterigmata and a basal simple septum, 30–36 × 4.5–6.5 µm; basidioles in shape similar to basidia, but slightly smaller. Basidiospores subglobose, with a distinct apiculus, thin-walled, colorless, smooth, occasionally with oil-drops, amyloid, CB–, 5.5–6.5 (–6.8) × (5–) 5.2–6.2 (–6.5) µm, L = 5.9 µm, W = 5.8 µm, Q = 1.01–1.02 (n = 90/3).

Additional specimens examined

China, Beijing, Haidian District, Jiufeng Forest Park, on dead Pyrus tree, 26 August 2022, He 7759 (BJFC 038896); Xiangshan Park, on dead Pyrus tree, 16 July 2022, He 7668 (BJFC 038804); Miyun District, Yunmengshan Scenic Spot, on dead Pyrus branch, 7 August 2021, He 7201 (BJFC 036518) & He 7203 (BJFC 036520) & He 7220 (BJFC 036537).

Notes

Scytinostroma beijingensis is characterized by having two kinds of gloeocystidia and short branched skeletal hyphae in hymenium, and growing on Pyrus. In the phylogenetic tree (Fig. 1), S. beijingensis formed a distinct lineage with strong support values that is sister to the clade comprising S. renisporum Boidin, Lanq. & Gilles, S. subrenisporum, S. acystidiatum Q.Y. Zhang, L.S. Bian & Q. Chen and S. caudisporum Boidin, Lanq. & Gilles. Scytinostroma renisporum differs from S. beijingensis by having cylindrical, subclavate or fusoid gloeocystidia (20–35 × 6–10 µm), ovoid to reniform basidiospores (5.2–6.5 × 3.2–4.8 µm) and a distribution in Côte d’Ivoire, western Africa (Boidin and Lanquetin 1987). Scytinostroma subrenisporum and S. acystidiatum can be easily distinguished from S. beijingensis by the absence of gloeocystidia (Zhang et al. 2023). Scytinostroma caudisporum is unique in the group for its distinctly large basidiospores (15–30 × 3–3.5 µm, Boidin and Lanquetin 1987).

Scytinostroma boidinii Yue Li, S.L. Liu & S.H. He, sp. nov.

MycoBank No: 848267
Figs 4, 5

Type

China, Beijing, Mentougou District, Xiaolongmen Forest Park, on dead angiosperm branch, 28 August 2020, He 6911 (BJFC 033860, holotype).

Figure 4. 

Basidiomes of Scytinostroma boidinii a He 6911 (BJFC 033860, holotype) b He 4985 (BJFC 024503) c He 7465a (BJFC 038600) d He 7465b (BJFC 038601). Scale bars: 1 cm (a–d).

Figure 5. 

Microscopic structures of Scytinostroma boidinii (from the holotype He 6911) a basidiospores b basidia c basidioles d gloeocystidia e skeletal hyphae from hymenium f skeletal hyphae from subiculum. Scale bars: 10 µm (a–f).

Etymology

Named to honor Dr. Jacques Boidin (Lyon, France) who contributed much to the taxonomy of Scytinostroma.

Fruiting body

Basidiomes annual, resupinate, widely effused, closely adnate, inseparable from substrate, membranaceous to coriaceous, first as small patches, later confluent up to 9 cm long, 3.5 cm wide, up to 300 µm thick in section. Hymenophore smooth, pale yellow (4A3), greyish yellow (4B4) to greyish orange [5B(3–4)], unchanged in KOH, not cracked; margin thinning out, adnate, fimbriate, white or concolorous with hymenophore surface. Context pale yellow.

Microscopic structures

Hyphal system dimitic. Context thickening, compact. Generative hyphae rare, scattered, simple-septate, colorless, slightly thick-walled, 2–3 µm in diam., IKI–, CB–. Skeletal hyphae dominant, colorless to yellow, distinctly thick-walled, moderately branched, 1.5–2 µm in diam., dextriniod, CB+. Catahymenium composed of skeletal hyphae, gloeocystidia, basidia and basidioles. Skeletal hyphae abundant, similar to those in the context, but strongly dextrinoid, dichotomous-branched with acute tips, 1–1.5 µm wide at lowest part. Gloeocystidia abundant, subcylindrical to subfusiform, colorless, slightly thick-walled, with or without contents, weakly SA+, 50–80 × 5–10 µm. Basidia subclavate to subcylindrical, thin-walled, colorless, smooth, with four sterigmata and a basal simple septum, 30–50 × 4–7 µm; basidioles in shape similar to basidia, but slightly smaller. Basidiospores subglobose, with a distinct apiculus, thin-walled, colorless, smooth, occasionally with oil-drops, amyloid, CB–, (4.5–) 5–5.5 (–6.5) × (4–) 4.5–5.5 (–6.2) µm, L = 5.1 µm, W = 5.0 µm, Q = 1.02–1.04 (n = 60/2).

Additional specimens examined

China, Beijing, Mentougou District, Lingshan Scenic Spot, on dead angiosperm branch, 10 April 2022, He 7465a (BJFC 038600) & He 7465b (BJFC 038601); Gansu Province, Tianshui County, Dangchuan Forest Farm, on dead Quercus tree, 9 August 2015, He 2499 (BJFC 020952); Hebei Province, Xinglong County, Wulingshan Nature Reserve, on dead angiosperm branch, 2 September 2017, He 4985 (BJFC 024503); Jilin Province, Jiaohe County, forestry experimental area, on fallen angiosperm trunk, 3 September 2017, He 5138 (BJFC 024656).

Notes

Scytinostroma boidinii is characterized by the relatively long gloeocystidia and subglobose basidiospores. In the phylogenetic tree (Fig. 1), S. boidinii formed a distinct lineage sister to S. alutum Lanq., which differs in having cracked basidiomes, slightly larger basidiospores (5–7 × 5–7.5 µm) and a distribution in France, Spain and Pakistan (Boidin and Lanquetin 1987; Bernicchia and Gorjón 2010). Scytinostroma yunnanense C.L. Zhao from Yunnan Province, southwestern China, has similar-sized basidiospores (4.5–5.5 × 4.2–5.2 µm) to S. boidinii, but differs in having white to cream hymenophore, smaller gloeocystidia (28–33 × 4–5 µm) and smaller basidia (21–28 × 4–5.5 µm, Wang et al. 2020).

Scytinostroma subduriusculum Yue Li, S.L. Liu & S.H. He, sp. nov.

MycoBank No: 848266
Figs 6, 7

Type

China, Beijing, Haidian District, Beijing Botanical Garden, on dead angiosperm branch, 15 July 2022, He 7657 (BJFC 038793, holotype).

Etymology

Refers to the morphological similarity and close phylogenetic relationship with S. duriusculum.

Figure 6. 

Basidiomes of Scytinostroma subduriusculum a He 7657 (BJFC 038793, holotype) b He 7134 (BJFC 036451) c He 7141 (BJFC 036458) d He 7148 (BJFC 036465) e He 7150 (BJFC 036467) f He 7717 (BJFC 036467). Scale bars: 1 cm (a–f).

Figure 7. 

Microscopic structures of Scytinostroma subduriusculum (from the holotype He 7657) a basidiospores b basidia c basidioles d gloeocystidia e skeletal hyphae from hymenium f skeletal hyphae from subiculum. Scale bars: 10 µm (a–f).

Fruiting body

Basidiomes annual, resupinate, widely effused, closely adnate, inseparable from substrate, membranaceous to coriaceous, first as small patches, later confluent up to 18 cm long, 3 cm wide, up to 160 µm thick in section. Hymenophore smooth, light yellow (4A4) to greyish orange (5B4), unchanged in KOH, not cracked; margin thinning out, adnate, fimbriate, white or concolorous with hymenophore surface. Context pale yellow.

Microscopic structures

Hyphal system dimitic. Context thickening, compact. Generative hyphae rare, scattered, simple-septate, colorless, thin-walled, 2–3 µm in diam., IKI–, CB–. Skeletal hyphae dominant, colorless to pale yellow, distinctly thick-walled, moderately branched, 2.5–4.5 µm in diam., dextriniod, CB+. Catahymenium composed of skeletal hyphae, gloeocystidia, basidia and basidioles. Skeletal hyphae abundant, similar to those in the context, but strongly dextrinoid, 1–1.5 µm in diam. Gloeocystidia abundant, subclavate to subcylindrical, colorless, thin-walled, usually with contents, SA+, 50–70 × 6–9 µm. Basidia subclavate to subcylindrical, slightly curved, thin-walled, colorless, smooth, with four sterigmata and a basal simple septum, 30–45 × 6–7.5 µm; basidioles in shape similar to basidia, but slightly smaller. Basidiospores subglobose, with a distinct apiculus, thin-walled, colorless, smooth, occasionally with oil-drops, amyloid, CB–, (6–) 6.2–7 (–7.5) × (5.5–) 5.8–6.8 (–7) µm, L = 6.5 µm, W = 6.3 µm, Q = 1.01–1.04 (n = 90/3).

Additional specimens examined

CHINA, Beijing, Changping District, Baiyanggou Scenic Spot, on dead angiosperm branch, 21 July 2021, He 7134 (BJFC 036451); Daxing District, Nanhaizi Park, on dead angiosperm branch, 31 July 2021, He 7148 (BJFC 036465); Fangshan District, Qinglonghu Park, on dead Sabina branch, 31 July 2021, He 7150 (BJFC 036467); Fengtai District, Yungang Forest Park, on dead Sabina tree, 25 July 2021, He 7141 (BJFC 036458); Haidian District, Bajia Country Park, on Sabina stump, 16 August 2022, He 7717 (BJFC 038853); Guangxi Autonomous Region, on dead angiosperm branch, 16 June 2016, He 3819 (BJFC022318); Guizhou Province, Libo Country, Xiaoqikong Scenic Spot, on dead angiosperm branch, 16 June 2016, He 3822 (BJFC022321); Hainan Province, Baoting Country, Qixianling Forest Park, on dead angiosperm branch, 18 March 2016, He 3590 (BJFC022090) & He 3593 (BJFC022092); Haikou City, Jinniuling Park, on dead twig of living Araucaria, 7 June 2016, He 3825 (BJFC022327); Wanning City, Xinglong Tropical Botanical Garden, on dead angiosperm branch, 19 March 2016, He 3603 (BJFC022101); Yunnan Province, Qiubei Country, Puzhehei Scenic Spot, on dead angiosperm branch, 26 July 2014, He 20140726-5 (BJFC019218) & He 20140726-6 (BJFC019219); Ruili City, Moli Tropical Rain Forest Scenic Spot, on fallen angiosperm trunk, 2 December 2015, He 3497 (BJFC021894). THAILAND, Chiang Rai, Mae Fah Luang University, on fallen angiosperm trunk, 21 July 2016, He 4045 (BJFC023484); Krabi, on dead angiosperm branch, 28 July 2016, He 4146 (BJFC023588). VIETNAM, Ho Chi Minh City Animal and Botanical Garden, on fallen angiosperm trunk, 4 September 2017, He 5204 (BJFC024722).

Notes

Scytinostroma subduriusculum is characterized by subcylindrical gloeocystidia, subglobose, relatively large basidiospores, and growth on both angiosperm and gymnosperm trees. It is widely distributed in China, and also found in Thailand and Vietnam. In the phylogenetic tree (Fig. 1), S. subduriusculum formed a distinct lineage sister to S. duriusculum (Berk. & Broome) Donk. There are 24 base pair differences between S. subduriusculum (He 4146, Thailand) and S. duriusculum (He 5748, Sri Lanka), and 66 differences between S. subduriusculum and S. duriusculum (CBS 757.81, France) of total 665 base pairs of ITS1+5.8S+ITS2 sequences. The similarities are 96.4% (He 4146 vs. He 5748) and 90.1% (He 4146 vs. CBS 757.81). The French samples may represent an undescribed species because their ITS1+5.8S+ITS2 sequences largely differ from those of Sri Lankan samples (71 differences of total 665 base pairs with only 89.3% similarity). Morphologically, the two species share subclavate to subcylindrical gloeocystidia and subglobose basidiospores. However, S. duriusculum has shorter basidia (20–25 µm) and smaller basidiospores (6–6.5 × 5.5–6 µm, measured from He 5748 from Sri Lanka).

Scytinostroma subrenisporum Yue Li, S.L. Liu & S.H. He, sp. nov.

MycoBank No: 848269
Fig. 8

Type

China, Guizhou Province, Libo County, Maolan Nature Reserve, on dead angiosperm branch, 11 July 2017, He 4792 (BJFC 024311, holotype).

Figure 8. 

Scytinostroma subrenisporum (from the holotype He 4792) a basidiomes b basidiospores c basidia d skeletal hyphae from hymenium e skeletal hyphae from subiculum. Scale bars: 1 cm (a); 10 µm (b–e).

Etymology

Refers to the morphological similarity and close phylogenetic relationship with S. renisporum.

Fruiting body

Basidiomes annual, resupinate, widely effused, closely adnate, inseparable from substrate, membranaceous to coriaceous, first as small patches, later confluent up to 10 cm long, 2.5 cm wide, up to 100 µm thick in section. Hymenophore smooth, pale orange (5A3), light orange (5A4) to greyish orange [5B(5–6)], unchanged in KOH, not cracked; margin thinning out, adnate, fimbriate, white or concolorous with hymenophore surface. Context pale yellow.

Microscopic structures

Hyphal system dimitic. Context thickening, compact. Generative hyphae rare, scattered, simple-septate, colorless, thin-walled, 2–3 µm in diam., IKI–, CB–. Skeletal hyphae dominant, colorless to yellow, distinctly thick-walled, moderately branched, 1.5–2 µm in diam., dextriniod, CB+. Catahymenium composed of skeletal hyphae, basidia and basidioles. Skeletal hyphae abundant, similar to those in the context, but strongly dextrinoid, moderately branched with acute tips, 1.5–2 µm wide at lowest part. Gloeocystidia absent. Basidia subcylindrical, slightly curved, thin-walled, colorless, smooth, with four sterigmata and a basal simple septum, 35–45 × 4.5–6.5 µm; basidioles in shape similar to basidia, but slightly smaller. Basidiospores ellipsoid to reniform, with a distinct apiculus, thin-walled, colorless, smooth, amyloid, CB–, (5.5–) 6–6.5 (–7) × (3.8–) 4–5 (–5.5) µm, L = 6.2 µm, W = 4.4 µm, Q = 1.35–1.45 (n = 60/2).

Additional specimens examined

China, Anhui Province, Qimen County, Guniujiang Nature Reserve, on dead angiosperm branch, 8 August 2013, He 1720 (BJFC 016187); Fujian Province, Wuyishan County, Wuyishan Nature Reserve, on dead angiosperm branch, 3 October 2018, He 5685 (BJFC 026747) & He 5686 (BJFC 026748); Guangxi Autonomous Region, Huanjiang County, Mulun National Nature Reserve, on dead angiosperm branch, 10 July 2017, He 4751 (BJFC 024270); Guizhou Province, Libo County, Maolan Nature Reserve, on angiosperm tree, 15 June 2016, He 3792 (BJFC 022291); Hunan Province, Guzhang County, Gaowangjie National Nature Reserve, on dead angiosperm branch, 3 August 2018, He 5626 (BJFC 026688); Jiangxi Province, Ji’an County, Jinggangshan Scenic Spot, on dead angiosperm branch, 11 August 2016, He 4303 (BJFC 023745); Lianping County, Jiulianshan Nature Reserve, on dead Liana branch, 14 August 2016, He 4384 (BJFC 023825); Yifeng County, Guanshan Nature Reserve, on dead angiosperm branch, 9 August 2016, He 4170 (BJFC 023612) & He 4199 (BJFC 023641).

Notes

Scytinostroma subrenisporum is characterized by the absence of gloeocystidia and ellipsoid to reniform basidiospores. In the phylogenetic tree (Fig. 1), S. subrenisporum is closely related to S. acystidiatum and S. renisporum. Scytinostroma acystidiatum that was recently described from China, is similar to S. subrenisporum by sharing the absence of gloeocystidia but differs in having smaller basidiospores (5.2–6 × 3.5–4.5 µm, measured from the type by the authors, Zhang et al. 2023). Scytinostroma renisporum is similar to S. subrenisporum by sharing ellipsoid to reniform basidiospores but differs by having cylindrical, subclavate or fusoid gloeocystidia and a distribution in Côte d’Ivoire, western Africa (Boidin and Lanquetin 1987).

Discussion

Previous studies showed that Scytinostroma is polyphyletic (Larsson and Larsson 2003). In this study, we performed phylogenetic analyses of Peniophoraceae based on ITS1-5.8S-ITS2-nrLSU sequences of samples of Scytinostroma s.s. and representative taxa of other genera. Species of Scytinostroma s.s. including the type, S. portentosum, formed a moderately supported clade in the likelihood analysis but a strongly supported clade in the Bayesian analysis. For the moment, we prefer to treat this clade as a monophyletic genus and believe that the support values could be higher if more samples of Peniophoraceae are included. Since a sequence of S. portentosum (type species, described from Pennsylvania) from Canada was distinct from the strongly supported sister lineage comprised of sequences of S. portentosum and S. hemidichophyticum from Europe, we suppose that all the European sequences represent S. hemidichophyticum and S. portentosum is restricted in distribution to North America. The two species, S. artocreas and S. incrustatum transferred from Michenera by Stalpers et al. (2021) based on morphological evidence, were nested within the Scytinostroma s.s. Scytinostroma duriusculum is a cosmopolitan species and has been reported from many countries in subtropical and tropical areas (Boidin and Lanquetin 1987; Bernicchia and Gorjón 2010). However, our phylogenetic analyses demonstrated that it could be a species complex, because three lineages were recognized from the samples of France, Sri Lanka, and China, Thailand and Vietnam.

On the one hand, species in Scytinostroma s.s. clade have some common morphological characters, for example, simple-septate generative hyphae, and ovoid, reniform to subglobose basidiospores with amyloid reactions in Melzer’s reagent. However, this doesn’t mean species with inamyloid basidiospores could not belong to Scytinostroma s.s. On the other hand, the shape of skeletal hyphae, presence of gloeocystidia and encrusted cystidia, and size of basidiospores varies in different species. Based on our phylogenetic and morphological study results, we recognized 14 species of Scytinostroma s.s.worldwide. Until now, seven species have been reported from China, all of which were newly described in the present study and other recently published papers (Liu et al. 2018; Wang et al. 2020; Zhang et al. 2023). It seems that China, especially its temperate areas, is rich in species diversity of Scytinostroma s.s. Although Scytinostroma s.s. is well studied in the present paper, the species diversity, taxonomy and phylogeny of Scytinostroma s.l. and related genera are still unresolved. A comprehensive study on this issue is urgently needed.

A key to species of Scytinostroma s.s. worldwide

1 Gloeocystidia absent 2
– Gloeocystidia present 3
2 Basidiospores > 6 µm long S. subrenisporum
– Basidiospores < 6 µm long S. acystidiatum
3 Basidiospores > 15 µm long 4
– Basidiospores < 15 µm long 6
4 Basidiospores fusiform to navicular S. caudisporum
– Basidiospores subglobose to globose 5
5 Lamprocystidia present, basidiospores 17–22 × 16–21 µm S. incrustatum
– Lamprocystidia absent, basidiospores 16–19 × 14–16 µm S. artocreas
6 Basidiospores ovoid to reniform S. renisporum
– Basidiospores subglobose 7
7 Distributed in subtropical and tropical areas 8
– Distributed in temperate areas 10
8 Gloeocystidia < 50 µm long S. yunnanense
– Gloeocystidia > 50 µm long 9
9 Reported from Sri Lanka, basidia 20–25 µm long, basidiospores 6–6.5 × 5.5–6 µm S. duriusculum
– Reported from China, Thailand, Vietnam, basidia 30–45 µm long, basidiospores 6.2–7 × 5.8–6.8 µm S. subduriusculum
10 Reported from occidental countries 11
– Reported from China 13
11 North American species S. portentosum
– European species 12
12 Skeletal hyphae in hymenium rarely branched S. alutum
– Skeletal hyphae in hymenium dichotomously branched S. hemidichophyticum
13 Gloeocystidia two kinds S. beijingensis
– Gloeocystidia one kind 14
14 Basidiospores > 6 µm in diam. S. subduriusculum
– Basidiospores < 6 µm in diam. S. boidinii

Acknowledgements

This study was supported by the National Natural Science Foundation of China (Nos. 32070005 & 32270014).

Additional information

Conflict of interest

No conflict of interest was declared.

Ethical statement

No ethical statement was reported.

Funding

National Natural Science Foundation of China.

Author contributions

Conceptualization, S.-H.H.; methodology, Y.L. and S.-H.H.; performing the experiment, Y.L., W.-Q.X. and N.Y.; formal analysis, Y.L. and W.-Q.X.; validation, Y.L., W.-Q.X., S.-L.L. and S.-H.H.; resources, S.-H.H.; writing—original draft preparation, Y.L. and S.-L.L.; writing—review and editing, S.-H.H.; visualization, Y.L.and S.-L.L.; supervision, S.-H.H.; project administration, S.-H.H.; funding acquisition, S.-H.H. All authors have read and agreed to the published version of the manuscript.

Author ORCIDs

Yue Li https://orcid.org/0000-0003-4091-1506

Wei-Qi Xu https://orcid.org/0009-0000-5675-386X

Shi-Liang Liu https://orcid.org/0000-0001-7556-2575

Ning Yang https://orcid.org/0009-0007-6900-5669

Shuang-Hui He https://orcid.org/0000-0003-4702-3034

Data availability

All of the data that support the findings of this study are available in the main text or Supplementary Information.

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